This invention relates to hand-held power screwdrivers.
In light gauge steel construction, an ordinary hand drill is used to drive a self-drilling screw. This practice creates many difficulties or limits to usage of self-drilling screws. These difficulties and limits are generally due to failure to satisfy one or more of three needs: support, force, and space. For example, members will move away if there is no support (FIG. 1A); need relatively large thrust force during drilling process (FIG. 1B); and need a clear space equal to size of a hand drill in front of a screwing surface (FIG. 1C).
More specifically, it is difficult to splice two thin plates with self-drilling screws--lack of support. (FIG. 2A) It is difficult to exert force, if you are on a ladder--lack of force.(FIG. 2B) And, it is difficult to attach metal studs to side of supporting structure--lack of space.(FIG. 2C)
My screwdriver (FIG. 3), comprising a body 50, a screwing arm 60, a clamping arm 70, and a clamping devise 80, is the solutions to the above three difficulties. My screwdriver clamps members 102 between a self-drilling screw 100 and clamping head 75 by hand gripping handle 81 and gripping lever 82. My screwdriver provides a rigid support to the two thin plates (FIG. 4A); my screwdriver provides a multiplied force, even if you are on a ladder (FIG. 4B); and my screwdriver does not require a large clear space in front of a screwing surface (FIG. 4C).
There are a few key points worth mentioning about my screwdriver. When an ordinary hand drill is used for screwing, the thrust force and the support are depended on external reactions and the gravitational force (weight), whereas, with my screwdriver both the thrust force and the support are within the same system. (FIG. 5A, 5B, and 5C)
Driving of a self-drilling screw 100 is three step processes: positioning 113, drilling 114, and screwing 115. A large thrust force is required only during the drilling process 114 that is generally short-distance (thickness of material) process. Multiplying the force for the short-distance is relatively easy task. (FIG. 6)
By bending the screwing arm, generally use of bevel gears and generally 90 degree, and by designing specifically for driving a screw, a screw can reach to "hard to reach" area. FIG. 7 shows the comparison of clear space requirements between an ordinary hand drill 103 and my screwdriver 105.
Several prior arts describe hand drills with clamping devises. They are U.S. Pat. Nos. 0,055,696 (1866) to Nevergold, 2,261,746 (1941) to Seaboly, 2,466,965 (1949) to Pitts, 2,642,761 (1953) to Goldberg, 3,250,153 (1966) to Purkey, 4,679,969 (1987) to Riley, 5,314,271 (1994) to Christiano, and 5,352,070 (1994) to Tehrani. However, these prior arts are for making holes, not for screwing, and they did not solve the difficulties and the limitations of using self-drilling screws as described here.
U.S. Pat. No. 2,079,863 (1937), to Koon describe screwing with clamp. However, this is not power screwdriver, and the screws used are for pre-threaded holes. And, this prior art did not solve the difficulties and the limitations of using self-drilling screws as described here.